1. Field of the Invention
This invention relates to an automatic transmission provided with planetary gear mechanism and engaging elements, such as clutches, and achieving plural number of driving gear positions, and more particularly to a connecting structure between a clutch drum and its adjacent members.
2. Description of the Prior Art
In an automatic transmission mounted on a vehicle, planetary gear mechanism and plural clutches or brakes as engaging elements are combined with each other, and a plural number of gear positions are achieved by a combination of the engagement and disengagement of these clutches and brakes respectively.
Accordingly, in the automatic transmission, the planetary gear mechanisms and engaging elements having friction plates, and plural rotary members for connecting these members are provided adjacently to each other.
It is necessary that these adjacently provided parts display their normal functions, and that the positions of the parts be controlled by securing predetermined widths of clearances among these parts so that these parts do not contact one another.
To carry out such position control operations, thrust bearings for securing the relative rotations of the parts are provided, whereby such clearances as mentioned above are secured in many cases.
For example, even in a transmission disclosed in Japanese Patent Application Laid-Open No. 63-270967, a clutch drum 35 of a clutch device 26 is rotated unitarily with a turbine shaft 12, so that the clutch drum is connected to the turbine shaft 12 by the meshing thereof with a spline. In such a meshed structure, the clutch drum 35 is displaced in the axial direction. Therefore, in order to control an axial position of the clutch drum, a thrust bearing 40 is provided between the portion of the clutch drum and a connecting member 39, and also a thrust bearing is provided between the part of the clutch drum and an adjacent member in the vicinity of a meshed part thereof with the turbine shaft 12.
Besides such techniques, a displacement control method of fitting a snap ring in a drum member of the clutch drum, and holding a relative member by the snap ring is also employed in practice.
However, providing thrust bearings on both sides of the clutch drum so as to carry out an axial position control operation as mentioned above causes first the necessity of securing spaces for providing the thrust bearings to arise, and such techniques also cause an increase in the manufacturing cost and number of man-hour of assembling work to occur due to an increase in the number of parts.
Also, in the method of carrying out this position control operation using a snap ring, a groove in which the snap ring for holding a relative member is to be fitted is formed in addition to a meshing portion with a friction plate. Therefore, the clutch drum requires to have a predetermined axial length, and an increase in the number of parts occurs.
The present invention has been made in view of the above circumstances, and provides an automatic transmission formed so as to control the axial displacement of rotary members, such as a clutch drum, without causing an increase in the manufacturing cost and number of man-hour thereof, and, moreover, without increasing the dimensions thereof.
According to an aspect of the present invention, the automatic transmission is provided with planetary gear mechanism and a clutch, a clutch drum and an adjacent rotary member having a unitarily rotatably connected structure owing to the spline meshing thereof, whereby plural gear positions are achieved, a first spline formed on one of the clutch drum and rotary member having a diagonally cut rising portion, a corner edge portion of a second spline formed on the other of the clutch drum and rotary member engaging the diagonally cut rising portion when the clutch drum is displaced in the axial direction thereof by a predetermined amount, whereby the position of the clutch drum is controlled.
Thus, an operation for controlling the displacement of the clutch drum can be carried out without causing an increase in the axial size, which was encountered in a related art automatic transmission due to the provision of thrust bearings and snap ring therein, of the automatic transmission according to the present invention, and without causing an increase in the part manufacturing cost and number of man-hour.
Especially, when the rotary member is a carrier supporting a pinion of the planetary gear mechanism, it is possible to form the second spline on an inner circumferential surface thereof, and form the first spline on an outer circumferential surface of an end portion of a hub portion of the clutch drum.
When the clutch drum is displaced toward the planetary gear mechanism, the diagonally cut rising portion of the first spline on the outer circumferential surface of the hub portion engages the corner edge portion of the second spline on the inner circumferential surface of the carrier to thereby restrict the displacement of the clutch drum.
Since the diagonally cut rising portion is formed in a step attendant to a process for the formation of the spline, a special process is not required.
When a groove for fitting a snap ring therein is formed in the section of the hub portion of the clutch drum, the length of the hub portion can be reduced by locating the groove at a position adjacent to a radially outer end of an inclined surface of the diagonally cut rising portion of the first spline, so that the overall axial length of the automatic transmission can be reduced.